Structural determinants of Actinomyces sortase SrtC 2 required for 1 membrane localization and assembly of type 2 fimbriae for 2 interbacterial coaggregation and oral biofilm formation 3 4 5

5 Chenggang Wu, Arunima Mishra, Melissa E. Reardon, I-Hsiu Huang, Sarah C. 6 Counts, Asis Das and Hung Ton-That* 7 8 Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, 9 Houston, TX, USA. 10 Department of Molecular, Microbial & Structural Biology, University of Connecticut Health 11 Center, Farmington, CT, USA. 12 13 These authors contributed equally to this work 14 15 *To whom correspondence should be addressed: 16 Hung Ton-That 17 Department of Microbiology and Molecular Genetics 18 University of Texas Health Science Center 19 6431 Fannin Street, R224/MSE 20 Houston, TX 77030, USA. 21 E-mail: [email protected]; 22 Tel. (+1) 713 500 5468; Fax (+1) 713 500 5499. 23 24 25 Running Title: Characterization of Actinomyces sortase SrtC2 26 27 28 29